1. Field of the Invention
The present invention concerns a chair, in particular an office chair or a school chair, with a tilt mechanism for inclining the seat surface of the seat with respect to the horizontal both in a forward/rearward direction of the seat surface and also in a right/left direction of the seat surface.
2. Technical Background
FIG. 1 is a diagrammatic side view showing a conventional chair 10 in which the present invention can also be used. The chair 10 substantially comprises a base structure 12 and a seat 14. The seat 14 usually comprises a seat surface 16 and a backrest 18, wherein the seat surface 16 and the backrest 18 can either be integral or separate from each other. The base structure 12 comprises in known manner a star-shaped base 20 which is supported movably or stationarily on base rollers or support feet 22, and a chair pillar 24 with integrated gas spring.
The seat surface 16 of the seat 14 is carried on a seat carrier 26 which is supported resiliently and adjustably in respect of height on the gas spring of the chair pillar 24 by way of a mounting means 28. Arranged between the seat carrier 26 and the mounting means 28 for the gas spring of the chair pillar 24 is a tilt mechanism 30, by means of which the chair 14 can be inclined in the forward/rearward direction of the seat surface 16.
FIG. 2 shows a view in greater detail illustrating the structure of a conventional tilt mechanism 30 for a chair 10 as shown in FIG. 1. The tilt mechanism 30 comprises in particular a first housing portion 32 which is fixedly connected to the seat carrier 26 and a second housing portion 34 which is fixedly connected to the mounting means 28 for the gas spring of the chair pillar 24. Arranged between the first and second housing portions 32, 34 are a pressure plate 36 and two spring blocks 38 of an elastically deformable material. At its top side (or optionally its underside) the pressure plate 36 has an approximately hemispherical conicity in the forward/rearward direction of the seat surface 16 about a pivot axis 36a, and the spring blocks 38 are also arranged in the forward/rearward direction of the seat surface 16, with respect to the pressure plate 36.
The seat 14 of the chair 10 can be inclined in the forward/rearward direction of the seat surface 16 by means of that conventional tilt mechanism 30, by virtue of the fact that the first housing portion 32 which is fixedly connected to the seat 14 by way of the seat carrier 26 is tilted about the pivot axis 36a by way of the conicity of the pressure plate 36, in which case, depending on the respective direction of tilt movement of the seat 14, the forward or the rearward spring block 38 is compressed by the first housing portion 32 against the rigidly arranged second housing portion 34. In that case the seat 14 is mounted resiliently by the spring blocks 38 comprising the elastically deformable material. Depending on the respective nature and purpose of use of the chair 10, it is possible to use special materials with respectively adapted characteristic curves for the spring blocks 38.
In addition DE-A-101 06 791 discloses a chair on which the classifying portion of claim 1 is based. That known chair has a tilt mechanism which permits inclination of the seat surface with respect to the horizontal both in the usual forward/rearward direction of the seat surface and also additionally in the right/left direction of the seat surface. In that case the tilt mechanism comprises a triangular-shaped pivotal mounting for the seat surface by way of spring elements to a support frame. Overall in that way the seat surface can be tilted in directions which differ by about 45° from the seat direction.